style: Animate offset-rotate.

Differential Revision: https://phabricator.services.mozilla.com/D32237

components/style/properties/longhands/box.mako.rs

@@ -390,7 +390,7 @@ ${helpers.predefined_type(
     "OffsetRotate",
     "computed::OffsetRotate::auto()",
     products="gecko",
-    animation_value_type="none",
+    animation_value_type="ComputedValue",
     gecko_pref="layout.css.motion-path.enabled",
     spec="https://drafts.fxtf.org/motion-1/#offset-rotate-property",
     servo_restyle_damage="reflow_out_of_flow"

components/style/values/computed/motion.rs

@@ -18,13 +18,25 @@ fn is_auto_zero_angle(auto: &bool, angle: &Angle) -> bool {
 }
 
 /// A computed offset-rotate.
-#[derive(Clone, Copy, Debug, MallocSizeOf, PartialEq, ToCss, ToResolvedValue)]
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    ToAnimatedZero,
+    ToCss,
+    ToResolvedValue,
+)]
 #[repr(C)]
 pub struct OffsetRotate {
     /// If auto is false, this is a fixed angle which indicates a
     /// constant clockwise rotation transformation applied to it by this
     /// specified rotation angle. Otherwise, the angle will be added to
     /// the angle of the direction in layout.
+    #[animation(constant)]
     #[css(represents_keyword)]
     pub auto: bool,
     /// The angle value.